Mouth-parts of Fly 



103 



makes a step downwards to the post-scutellum, which 

 exhibits 011 its dorsal surface a pair of phxtes ; these 

 meet along- the middle line, and have together an 

 oval outline. Below, the mesothorax swells into 

 a great hemispherical prominence, the mesosternum, 

 which is convex downwards, its dejDth allowing a great 

 prolongation of the vertical mesothoracic muscles. The 





/^' 



Fig. 74. — Horizontal section tlirougli meso- and metathorax of pupa 

 (enclosed in larva), mf, medifurca. Im, Im', remains of larval muscles 

 as yet unabsorbed, the posterior series being those of the metathorax 

 and indicating the extent of that segment, vm, vertical muscles. 



intermediate legs are attached to the hinder part of the 

 mesosternum by oval sockets. 



The metathorax is small in comparison with the meso- 

 thorax. On its side may be seen the posterior thoracic 

 spiracle, and above it the haltere, or rudimentary hind- 

 wing. On the dorsal surface there is a small metathoracic 

 plateau, on either side of the post-scutellum and at a 



